Transformer



y 6, 1941- \v G. B. HORN 2,241,261

TRANSFORMER Filed May 29, 1940 ,INVENTOR G'mrge 5. Horn ATTORN EYS Patented May 6, 1941 UNITED STATES PATENT OFFICE TRANSFORMER George B. Horn, Fairfleld, Conn., assignor to Wheeler Insulated Wire Company, Bridgeport, Conn., a corporation of Connecticut Application May 29, 1940, Serial No. 337,873

8 Claims.

The present invention relates to a transformer, and, more particularly, to a transformer for operating a plurality of fluorescent tube lamps.

In operating, for example, a pair of fluorescent tube lampsfrom a pair of secondaries carried by the operating transformer, trouble has been encountered, for, when one lamp is in operation and the starter circuit closed to heat the filaments of the other lamp, the leakage reactance caused thereby will affect the secondary connected to the first tube and reduce the voltage therein below the critical value to cause the tube to become nonconductive and consequently extinguished. v

Efl'orts have been made to overcome this difflculty by winding the secondaries about one another so as to reduce the effect of the leakage reactance under these conditions. These, however, have resulted in a large square-type transformer which could not be readily adapted to the small space requirements of the transformers for operating such tubes.

According to the present invention, these dimculties have been overcome by providing a thin,

fiat transformer in which the leakage reactance in the secondaries have little or no effect upon one another so that either or both of the lamps can be operated without interfering with one another.

This is accomplished by providing an elongate core and disposing the primary of the transformer intermediate the ends of the core and the secondaries at either end of the primary and in widely spaced relation with one another. In each of the secondary circuits there is connected a fluorescent tube and starting mechanism therefor. With the secondaries so positioned and connected to the tubes, the leakage reactance caused by the starting current will not, because of the widely spaced relation of the secondaries, interfere with'the operation of the tubes.

In the preferred form of the invention, the transformer core is made up of L-shaped laminations to form a rectangle with two longitudinally extending legs connected at their ends. The primary of the transformer consists of a pair of electrically connected coils each positioned about one of the legs and spaced midway between the ends. The two secondaries are located on the core, one at each end, and are each made up of a pair of electrically connected coils which are positioned on the core with a coil of each pair disposed about a leg of the core. By dividing the primaries and secondaries into a plurality of coils, a very small, flat transformer is obtained which can be readily employed in th small space available in lighting units of this type.

While the transformer may be connected in many ways to produce the desired voltage for operating the fluorescent tubes, I have found it desirable to connect the secondaries in the circuit with the primaries so as to form an autotransformer energized from the line. By this arrangement, I am able to accurately supply the proper voltage to the tubes and to secure substantially the same current in each tube without the use of compensating induction coils as are now required.

Other features and advantages of my invention will be apparent from the specification and claims when considered in connection with the drawing, in which:

Figure '1 shows a top plan view of the transformer.

Fig. 2 is an end'view of the transformer.

Fig. 3 is a diagrammatical showing of the electrical circuit employing the transformer for operating a pair of fluorescent tube lamps.

Th transformer of the present invention is primarily used for energizing fluorescent tube lamps. I have shown in Fig. 3, a pair of fluorescent lamps l0 and II having the filaments Illa, "lb and Ila, Ilb connected in series with the starter switches I00 and 0, each energized from the transformer 12. Heretofore it has been difllcult to operate two of these lamps at the same time from the same transformer due to the fact that when one lamp is energized and the starting switch for the other lamp is closed to heat the filaments for that lamp, the leakage reactance caused by the starting current would reduce the voltage in the other secondary and cause it to become less than the critical voltage required for the tube and thus extinguish the lamp.

In order to overcome this difficulty, it has been proposed that the transformers be arranged with their secondaries mounted one on the other to reduce the efiect of the leakage reactance. This, however, produces a large, bulky transformer which could not be satisfactorily used in the limited space available in the mountings of these florescent tubes.

According to the present invention, I have provided a transformer which overcomes the objectionable effect of the leakage reactance while at the same time being of sufficient size to enable it to be readily used with fluorescent tubes.

As shown in Figs. 1 and 2, the transformer of the present invention is relatively long, narrow and flat so that it can readily be fitted into a casing or support for a fluorescent tube lamp, which tubes are of a substantial length.

The core l3 of the transformer is made up of a plurality of L-shaped laminations H interfltted as shown in Figs. 1 and 2 to produce a rectangular core having two longitudinally extending legs joined at their ends.

As is shown in Figs. 1 and 3, the primary I5 01' the transformer comprises a pair of coils iia and I5!) electrically connected together, with each of the coils disposed about one of the longitudinally extending sides of the core and substantially midway between the ends of the core.

The electrical connection between the two coils is protected by a sheath of insulating material I6.

A pair of secondaries I1, I8 are provided on the transformer and are positioned at each end of the primary so that they are spaced a substantial distance from one another on the core. Each of the secondaries comprises a pair of coils 11a, Nb and Illa, l8b. The coils of each secondary are electrically connected together, with their connections covered by sheaths I8, 20 and are positioned about the longitudinally extending legs of the rectangular core, as shown in Fig. 1.

By splitting the primaries and secondaries into a plurality of coils positioned about the sides of the core, I have been able to reduce considerably the size of the transformer.

As is shown in Fig. 3, the primary I5 is connected across the suitable source of A. 0. current. The secondary I! has one terminal connected to a common terminal on the primary coil, and its other terminal connected to the filament Illa at one end of the tube Ill through the starter switch to the other filament lb of the tube l0 which is connected to the other terminal of the primary coil.

Also, the'secondary I! has one end connected to the common terminal of the primary coil and the other terminal connected to filament Ila of the lamp ll, through the starter switch lie to the other filament l lb which is connected to the other terminal of the primary.

In the circuit for one of the tubes, a condenser 2| is connected to provide a suitable power factor correction as required by utility companies, and also may reduce stroboscopic effect in the lamps.

With the secondary circuit thus connected, it will be apparent that an autotransformer is formed in which the primary and secondaries are connected so as to be energized from the line. This produces a very desirable transformer for supplying the required voltage for operating the tubes.

With other circuits now in use, the tube circuit having the capacity inserted therein carries a starting current about half its normal value when the starting switch Inc is closed and a compensator coil is necessary to build up the starting current in the circuit to a value sufllcient to cause the filaments to be lighted. The circuit arrangement of the present invention, however, provides a sufficiently large starting current to each of the two tubes without the necessity of supplying a compensator in the circuit having the leading current therein. I

The tube circuits are normally inoperative to pass current. When it is desired to illuminate the tube I0, starter switch lllc is closed, thus ments Ilia and llb to cause them to become heated, and, when they have been heated to a proper temperature the starter switch is then opened thereby causing an electron flow which will, in effect, close the circuit between the filaments and illuminate the tube. The tube will continue to operate so long as a proper voltage to maintain the flow of electrons is impressed upon the tube.

When it is desired to energize tube II, the switch He is closed and the current for heating the filaments passes therethrough. The leakage reactance caused by this passage of current through the secondary coil II will not have any effect on the spaced secondary I1 so as to reduce the voltage therein. As soon as the filaments Ila and llb have been heated to a proper temperature, the switch He is open and the electron flow is set up between them, and the circuit is maintained between the filaments by the proper voltage being impressed thereon.

Thus, it will be seen by providing the two coils in spaced relationship on the core I have not only produced a transformer 01' a size which can readily be used with fluorescent lights of the type described, but one which, because of this spacing. has eliminated all appreciable effects of the leakage reactance present during the starting of these fluorescent lamps so that either lamp can be operated or both operated simultaneously.

While I have described the primary and secondaries as being made up of a plurality of secondary coils, it is to be understood that these can be made as single coils so long as the secondaries at which time current flows through the two lilaare disposed at either end of the primary in spaced relation with one another so as not to be affected by the leakage reactance in either secondary circuit.

Variations and modifications may be made within the scope of this invention and portions of the improvements may be used without others.

I claim:

1. A transformer for operating a plurality of separately operable fluorescent tube lights comprising an elongate core; a primary coil positioned on said core intermediate the ends thereof; and a pair oi secondary coils positioned on the core, one at each end thereof, each of said secondaries being connected to the primary to form an autotransformer and having means whereby each secondary is connected to one of the fluorescent tube lights, the spacing between the secondaries being suilicient to prevent leakage fiux of one secondary from acting on the other secondary to affect the operation of the tube connected thereto.

2. A transformer for operating a plurality of separately operable fluorescent tube lights comprising an elongate core having parallel side legs; a primary comprising a pair of interconnected coils positioned, one on each leg of said core intermediate the ends thereof; and a pair of secondaries, each comprising a pair of interconnected coils positioned on the legs oi the core, one pair at each end thereof, each of said secondaries being connected to the primary coil to form an autotransformer and having means whereby each secondary can be connected to one of the fluorescent tube lights, the spacing between the secondaries alone being sufiicient to prevent leakage flux of one secondary from afiecting the other secondary to alter the voltage therein and adapted to be impressed on its connected light.

3. In combination with a pair of fluorescent accuser tubelights having an operating circuit for each of said lights; a transformer having an elongate core and a plurality of coils mounted on said core and connected together and across a power supply line to form an autotransformer, the coils adjacent each end of the core being connected in one of the operating circuits for the fluorescent tubes to provide spaced secondaries for operating said tubes, the spacing between the secondaries being suflicient to prevent leakage flux of one secondary from acting on the other secondary to affect the operation of the tube con.- nected thereto; and a condenser in one of said tube circuits to provide for power factor compensation, said transformer alone automatically supplying substantially equal starting current to the tube circuits to start the operation of the tube, said condenser also tending to reduce the having an elongate core and a plurality of coils mounted on said core and connected together and across a power supply line to form an autotransiormer having a primary and a plurality of secondaries. each secondary being disposed at opposite ends of the primary coil and connected to one of the fluorescent tubes for operating the tubes, the spacing between the secondaries being suiilcient to prevent the leakage flux of one secondary from aifecting the other during starting of the tube. connected thereto while the other tube ts in operation.

8. In combination with a plurality of separately operable fluorescent tube lights, each having a pair of spaced fllaments and a starter circuit including a switch, for heating said filaments to render the tube conductive, an autotransformer for operating said tubes including a primary coil and a plurality of secondary coils each connected to a tube, said secondaries being disposed on the transformer at opposite ends of the primary coil, the spacing between said secondary coils being suflicient that leakage reactance in one secondary caused by the closing of the starter switch will not aflect the other secondary to alter the voltage impressedon its connected fluorescent tube. I

7. In combination with a, pair of separately operable fluorescent tube lights, an elongate auto- -transformer having a pair of secondaries located at each end thereof for connection to said fluorescent tubes, said secondaries being so spaced apart on the transformer that the spacing alone prevents leakagereactance of one from aiIecting the other.

8. In combination with a plurality of separately operable fluorescent tube lights, an autotransformer having a' primary and a plurality of separate secondaries, each secondary being positioned at the opposite ends of the primary and connected into a circuit for one of the fluorescent tubes, the spacing between the secondaries being suflicient to prevent leakage flux of one secondary from acting on the other secondary to affect the operation of the tube connected thereto: at least one of said circuits for the fluorescent tubes having a condenser in series therein for power factor compensation, said transformer alone supplying substantially equal starting current to all of said fluorescent tube circuits to start the operation of said tubes.

Gnomes a. norm. 

